Here is the full list of all 15 One Troll Army achievements.
Kill 1000 enemies.
Complete all remaining quests.
Hire 30 mercenaries.
Upgrade tower weapons to the maximum level.
Improve all troll skills to the maximum level.
Spend 10000 gold on resources.
Kill the most powerful of the bosses.
Earn 10000 materials in total.
Survive at least 30 waves without losses at the Survival mission.
Upgrade goblins to the maximum level.
Upgrade all buildings and towers up to level 3.
Earn 10000 coins in total.
Upgrade all buildings and towers up to level 2.
Complete all buildings and towers of the fortress.
Kill 100 enemies.